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Tissue Type Test

Test Overview

A tissue type test is a blood test that identifies
substances called
antigens on the surface of body cells and tissues.
Checking the antigens can tell if donor tissue is safe (compatible) for
transplant to another person. This test may also be called HLA typing. Antigens
can tell the difference between normal body tissue or foreign tissue (for
example, tissue from another person's body). Tissue type helps find the best
match for tissues or blood cells (such as
platelets). In some cases, a tissue type test may be
done to see whether a person has a chance for developing certain diseases that
cause the body to attack its own cells, such as
autoimmune diseases.

A special pattern of
antigens (called tissue type) is present on each person's cells and tissues.
Half of each person's antigens come from (inherited) the mother and half from
the father. Identical twins have the same pattern, but everyone else has his or
her own special pattern. Brothers and sisters have a 1-in-4 chance of having an
identical match. Each person's antigen pattern can be "fingerprinted" through a
tissue type test.

The closer the match of antigens, the more
likely that an organ or tissue transplant will be successful.

The more similar the antigen patterns are from two
people, the more likely it is that they are related.

Two main antigen groups are used for a tissue type test.
Class I has three classes of antigens (HLA-A, HLA-B, HLA-C) that are found on
some kinds of blood cells. Class II has one class of antigens (HLA-D) that are
found only on certain cells in the body. There are many different types of
antigens in each category.

Why It Is Done

A tissue type test is done to:

See if the antigen pattern for donated tissue or
organs (including a blood platelet transfusion or bone marrow transplant) is a
match. The success of a transplant depends on how closely the antigen patterns
match. The antigen patterns are most likely to be similar when the donated
organ or tissue comes from a close relative of the person.

See how
likely two people are related. If the antigen patterns are very similar, they
are likely to be related. But a tissue type can't prove definitively that two
people are related. A tissue type test may be done as part of a paternity test
to check to see if a man could be the father of a child.

Find
people who may have a high chance of certain autoimmune diseases.

How To Prepare

If you are donating tissue or blood
cells, your doctor may want to talk about your medical history—such as a
history of cancer, infections, high-risk behaviors, use of drugs, exposure to
toxins, and foreign travel. This may be important in understanding whether your
donor tissue can be used.

How It Is Done

The health professional drawing blood
will:

Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.

Clean the needle site with
alcohol.

Put the needle into the vein. More than one needle stick
may be needed.

Attach a tube to the needle to fill it with
blood.

Remove the band from your arm when enough blood is
collected.

Put a gauze pad or cotton ball over the needle site as
the needle is removed.

Put pressure on the site and then put on a
bandage.

How It Feels

The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch.

Risks

There is very little chance of a problem from
having a blood sample taken from a vein.

You may get a small bruise at the site. You
can lower the chance of bruising by keeping pressure on the site for several
minutes.

In rare cases, the vein may become swollen after the
blood sample is taken. This problem is called phlebitis. A warm compress can be
used several times a day to treat this.

Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (such as Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.

Results

A tissue type test is a blood test that
identifies substances called
antigens on the surface of body cells and tissues.
Checking the antigens can tell if donor tissue is safe (compatible) for
transplant to another person.

For organ or tissue transplants, the results of
tissue type show whether the donated tissue matches. The antigen pattern match
is different for each type of transplant. For example, the match for a bone
marrow transplant needs to be closer than the match needed for a kidney
transplant.

To check family relationships, the more alike the
antigen patterns are, the more likely it is that the two people are
related.

If an antigen related to a disease is found, that disease is likely to be present.

What Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include having had a blood
transfusion in the past 3 days.

What To Think About

A tissue type test is more useful than a blood
type to see if two people may be related. Although tissue type cannot prove
that two people are related, it can show how likely it is that they are
related. Tissue type may be done as part of a lawsuit when blood relation is an
issue. For more information, see the topic
Blood Type.

A genetic test looks at a
DNA sample for genes or to analyze the number,
arrangement, and characteristics of the chromosomes.

Having an antigen
pattern that is linked with certain diseases does not mean that the disease is
present or will definitely develop. Your doctor will talk to you about the
chance for developing the disease.

A person who wishes to be a
possible tissue donor (such as a bone marrow donor) generally has a tissue type
test. The person's antigen pattern is kept on file in a tissue donor bank and
checked to see if it matches anyone needing a transplant.

There are
registries of people who have had tissue typing done and who offer to be donors
to anyone in need.

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How this information was developed to help you make better health decisions.